Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover read-only, idempotent, open-world, non-destructive behavior, so the description's added value here is real: it discloses the daily per-caller quota and the payment mechanics (X-Payment / X-Payment-Tx / Bearer fg_… must go in the MCP headers, not the arguments). Auth placement is exactly the kind of thing an agent cannot infer from structured fields, though rate-limit specifics and error behavior remain unstated.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The lead English sentence is well front-loaded, but the body repeats the same content three times (English summary, [zh] block, [en] block), and the payment sentence is appended with no structural separation. The duplication costs tokens without adding information.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a two-parameter read-only tool with no output schema, the description covers the essentials: what is returned (median, dispersion bps, verdict, valid source count), that it is free with a quota, and how payment is authenticated. The remaining gap is symbol/quote formatting, which matters because the schema has zero field descriptions.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0% and there are no field descriptions, so the description must carry parameter meaning. It only says symbol is required and quote is optional — something the schema's required list and default:null already convey — and adds no symbol format (e.g. BTCUSDT vs BTC/USD), no default quote value, and no effect of quote on the returned median.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a concrete verb+resource: it computes a median consensus price across sources and returns dispersion in bps plus a verdict (tight / wide / divergent). That is far more specific than the name alone and hints at the split from price-consensus.source_detail, though the sibling is never named.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Framing the use case as "ask 'what is the true price across sources'" implies when to reach for it, and the free-tier note implies a quota-driven context. However, there is no explicit when-not guidance and no routing to source_detail or other siblings.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.